1. Field of the Invention
The present invention relates generally to the field of surgery and post-surgical radiation for the treatment of cancer. Specifically, the present invention relates to the field of breast brachytherapy for the adjunctive treatment of breast cancer.
2. Description of the Related Art
Breast cancer patients receiving a partial mastectomy (lumpectomy) with or without axillary sampling of lymph nodes are given radiation therapy to the remaining breast tissue of the cancerous breast as an integral and essential element for the ablation of any remaining residual undiscovered microscopic foci of cancer.
Today, the delivery of adjuvant radiation to the surgically treated breast is done utilizing either whole breast radiation or brachytherapy (limited field) radiation.
Whole Breast Radiation:
Whole breast radiation has been the standard method of adjuvant breast radiotherapy employed until relatively recently. It has been shown to be extremely effective in preventing breast cancer recurrence in women treated with conservative breast surgery (“Limited Field Radiation Therapy in the early Stage of Breast Cancer”. The Journal of the National Cancer Institute: Vol. 95, 16). However, whole breast adjuvant radiation is associated with patient morbidity that is seen in both the acute (at or near the time of radiation treatment) and chronic time periods (months to years after treatment has been given). Any tissue within the field of treatment can be adversely affected; this includes the skin, muscles, bone, heart, and lung; as an example, acute morbidity can include skin burn and a chronic sequela is sarcomatous cancer arising in previous irradiated tissue years after treatment. Now, questions have also arisen regarding the need and/or efficacy of treating all breast tissue in the involved breast. Comparison of patients receiving whole breast radiation versus limited field radiation to the lumpectomy site showed the following results over a five year period: there is no difference in the median time to recurrence or rate of local recurrence regardless of mode of radiation therapy i.e. whole breast versus limited field, and that there is no difference between groups in rate of overall survival, disease free survival or in the rate of distant spread of the cancer (beyond the breast). An additional shortcoming in the delivery of standard whole breast radiation to the surgically treated breast requires the delivery of this treatment course over an extended period of time (5-6 weeks on average). Because of this, patient compliance consisting of a daily five-day course of radiation treatment (weekends and holidays excepted) for an extended period of 5-6 weeks is the norm. This regimen is burdensome to many rural and elderly patients who cannot economically or practically commute to a treatment center or who, because of age or disability, cannot meet these requirements for treatment. The result of this inability to undergo whole breast radiation treatment results in the total surgical excision of the breast, a mastectomy.
Brachytherapy:
Recently, limited field radiation therapy, known as brachytherapy, has been shown to be an effective method of delivering radiation therapy to patients who have undergone breast-conserving surgery (“Limited Field Radiation Therapy in the early Stage of Breast Cancer”. The Journal of the National Cancer Institute: Vol. 95, 16). Because of the present day inability to definitively surgically eradicate all cancer bearing tissue at the site of operation in the breast, radiation treatment is delivered to the site of surgical excision to incorporate a 2-3 cm rim of normal appearing tissue on all sides of the surgical cavity. All remaining breast tissue is not irradiated. Treatment performed utilizing brachytherapy as an adjunct to the surgical excision of a breast cancer is done in a markedly shortened treatment interval (five day limited field radiation schedule versus five weeks whole breast) and, because of this, will provide those patients unable to undergo a four to six week treatment regimen of whole breast radiation an alternative treatment choice other than total mastectomy. And, because of the methodology used, only the breast tissue at greatest risk of recurrence is treated thereby reducing the morbidity seen in the whole breast radiation treatment.
Even the application of brachytherapy to the cancerous bed of resected lumpectomy specimens has undergone a genesis since its inception. It is delivered, at present, using one of two techniques. The first technique employs the percutaneous placement of multiple treatment rods through the breast in a configuration that allows for the delivery of a specific radiation dose to a specific area of residual targeted breast tissue in the post lumpectomy patient. Multiple skin entrance and exit sites are created with resultant scarring and, because of the need for multiple delivery devices, patient acceptance is limited. An alternative method for Brachytherapy treatment utilizes a catheter device that is placed into the surgically excised bed either operatively or post-operatively allowing for the delivery of a five-day course of radiation treatment. Because the Proxima brachy catheter device (Proxmia Therapeutics Inc., Alpharetta, Ga.) relies on a distensible balloon for placement within the surgical cavity prior to delivery of treatment, a spherical surgical cavity is required. However, the surgical excision of a breast cancer is not performed in a standardized manner because breast cancers by their very nature do not grow and proliferate exactly alike. Examples of breast cancer geometries include spherical, stellate (radiating arms of breast cancer proliferation of unequal length extending unequally in various directions), and linearly directed (breast cancers growing along the axis of a specific duct). These examples hint at the variability of size and shape of cancers encountered routinely during surgical excision. And so the cancer is excised in a blind fashion by excising tissue by feel; this results in a jagged cavity of uneven dimensions which must then be made circular by approximating the cavity circumference around the spherical applicator balloon. The spherical device can not precisely occupy the surgically excised tumor bed and requires further surgical manipulation and fixation of tissues in non-anatomical positions to achieve this goal. In other words, the surgeon in utilizing this mode of therapy must reconfigure the surgical cavity to “fit the device”.
The creation of any surgical cavity, by necessity, will form a deformity in the tissue bed from which it is excised. The result is an anatomic deformity that may or may not be apparent on the skin surface. The deformity created in the breast by excision of tissue, whether for benign or malignant disease, is a routine consequence of breast surgery. This defect, however, is markedly compounded by the addition of radiation therapy, whether by whole breast or limited field application. And it is further compounded by the surgical reapproximation and reshaping required for the proper seating of brachytherapy delivery devices that utilize a fixed shape. (The breast, as a skin appendage, is important functionally, aesthetically and is of paramount importance in a personal sense to a healthy body image.)
Radiation Dose Delivery:
Radiation dose delivery to targeted tissue is determined by the physics inherent in the production of radioactive or highly energetic photon energy. Delivery of a specific dose to a targeted area is also dependent on the ability to fix the delivery device (a stable platform) so that each successive treatment adds a further increment of radiation energy only to the targeted tissue. Any change in delivery device position can result in either over or under treatment to the area of targeted tissue or the adjacent tissue, i.e., skin, muscle, or non-targeted breast; this will cause morbidity to surrounding structures. Furthermore, the necessity of surgically shaping breast tissue around a delivery device can result in an area of tissue requiring treatment of being excluded because of the anatomic disruption caused by this additional surgical maneuver.
Notwithstanding the foregoing, there remains a need for improved methods and devices for use in targeted brachytherapy of soft tissue.